The present invention relates to an inflator for a safety system used in a motor vehicle or the like, and more specifically to an improvement in a hybrid inflator.
With the development of an inflator for an inflating-type safety system of a motor vehicle, a hybrid inflator using both a pressurized gas and a solid gas generating agent is attracting attention. A main design requirement for a hybrid inflator is that the inflator inflates an air bag by a predetermined amount in a predetermined time so that the air bag is effectively activated. Various proposals concerning a structure to meet the requirement have heretofore been made (for example, as referred in JP-A No. 8-282427).
Since such a hybrid inflator has generally a complicated internal structure, it is necessary to manufacture the inflator with a sufficient care in order to enhance reliability and it is necessary to mount the inflator to a vehicle securely in order to activate the inflator without fail. Particularly in a hybrid inflator, since there are a relatively large number of parts and a robust housing is required for accommodating a pressurized gas, the inflator itself becomes relatively heavy, and there is a room for improvement in mounting easiness to a vehicle. Also, since hybrid inflators are mounted to various vehicles such as automobiles or the like, it is necessary to maintain intended activation performances thereof regardless of vibrations from the vehicles even after mounted.
Furthermore, in order to improve mounting easiness to various vehicles, preferably, the entire weight and size of an inflator are suppressed and such a structure that the inflator can be mounted to a vehicle easily and securely is employed.
The present invention is made in order to solve the above problem, and an object thereof is to provide an inflator having a structure such that it can be mounted to an air bag module more easily and securely than a conventional inflator, and that can be manufactured simply and is improved in reliability at the time of activation.
According to the present invention, an inflator, which is a device for inflating an air bag of a vehicle, can be prevented from being dislocated and can be mounted on a vehicle securely is provided.
That is, the present invention provides an inflator comprising, in a cylindrical inflator housing elongated in an axial direction and containing a gas generating material for inflating an air bag and an activation assembly for generating an activation gas to activate the gas generating material, and provided, in an axial end of the inflator housing, with a diffuser assembly which is cylindrical in shape with an end and has a plurality of outlet holes in a peripheral wall surface thereof. A through-hole is formed in the end surface of the diffuser assembly, a stud bolt for fixing the inflator is inserted into the through-hole and the stud bolt is fixed by a flange portion provided on an end portion thereof.
The diffuser assembly may be formed in such a manner that the end surface thereof is provided with the through-hole after a cylinder with an end is formed, or alternatively, in such a manner that one end opening (in other words, an opening in the end surface side) of a substantially cylindrical in shape is crimped inwardly to have a flange-shaped shape.
The stud bolt can be fixed by a flange portion provided at its end portion. For example, the flange portion of the stud bolt may be welded to the inside of the end surface of the diffuser assembly, or a supporting portion projecting inwardly in the radial direction can be formed on an inner peripheral surface of the diffuser assembly so that the flange portion of the stud bolt can be held between the supporting portion and an end surface of the diffuser assembly. Particularly, the latter case is suitable for a case such that the end surface is formed by crimping an end opening of the diffuser assembly positioned in the side where the stud bolt is supported. The supporting portion has to be formed at least to support the rear end of a flange portion in the stud bolt. For example, the supporting member may be formed in such a manner that a projection is formed at a arbitrary position circumferentially in the inner peripheral surface of the diffuser assembly, or alternatively, in such a manner that the inner peripheral surface of the diffuser assembly is circumferentially step-notched. Naturally, the supporting portion may be also formed in such a manner that the inner peripheral surface of the cylindrical diffuser assembly is hollowed circumferentially from an end portion in the predetermined width and then, the inner peripheral surface of the cylindrical diffuser assembly is provided with a bump.
Further, when the stud bolt is fixed by a method other than a welding, it is preferable that rotation between the stud bolt and the diffuser assembly is prevented. For this purpose, desirably, a rotation-preventing structure for preventing circumferential rotation such as a notched structure formed in the radial direction is provided on the flange portion of the stud bolt.
Generally, the inflator is accommodated in the module case together with an air bag for introducing an activated gas to inflate the air bag, and the module case is mounted to various vehicles. In case of the above inflator elongated in the axial direction, the inflator and the module case are fixed to each other by the stud bolt provided at an end surface of the inflator or the like, and the stud bolt is welded to the diffuser assembly provided on an end surface of the inflator housing from the outside. In the present invention, the flange portion is provided on an end portion of the stud bolt (in other words, a rear end portion existing inside the diffuser assembly after mounted), the through-hole is provided in the end surface of the diffuser assembly and the stud bolt is inserted from the inside of the through-hole. With this structure, the flange portion formed in the rear end portion of the stud bolt is abutted against and supported by the inner surface of the diffuser assembly. By arranging the stud bolt to the inflator in this manner, connection between the stud bolt and the inflator can be maintained securely at the time of or after mounting the inflator to the module case with the stud bolt, and thereby, the inflator can be prevented from being dislocated from the module case.
The above inflator can be mounted to the module case in such a manner that the stud bolt is protruded from the module case and then, a nut is fastened to the protruded stud bolt. In this case, it is preferable to provide a rotation-preventing means at the time of assembling the inflator since, without any rotation-preventing means of the inflator, the inflator starts rotating inside the module case by fastening the nut and the assembling process is disturbed. Such a rotation-preventing means can be obtained, for example, in such a manner that a flat surface is formed by notching the predetermined part in the peripheral surface of the stud bolt, a hole of the module case which the stud bolt passes through is formed to meet the flat surface of the stud bolt and both are combined with each other. In this case, the stud bolt has to be notched in the predetermined shape. Preferably, the rotation-preventing means is provided in the activation assembly side of the inflator, more particularly, on the peripheral edge of a boss member which closes one end of the inflator housing and stores an electrical ignition type igniter to be activated by the activation signal.
In other words, the diffuser assembly, which is cylindrical in shape with a bottom and has a plurality of outlet holes in the peripheral wall surface, is arranged on the one axial end portion of the inflator housing, and the boss member, which stores an initiator for activating the inflator, is arranged on the other end portion. Further, the stud bolt for mounting the air bag module is provided in the diffuser assembly. In the boss member, the peripheral edge is formed like a flange protruding in the radial direction of the housing. The rotation-preventing means, which is required at the time of mounting the inflator to the air bag module, is provided on the above peripheral edge. An example of the rotation-preventing means is a protruding portion formed on the flange-shaped peripheral edge and projecting partially outward in the radial direction. If the rotation-preventing means for mounting the inflator is provided to the boss member in this manner, the stud bolt is not required to be cut and a stud bolt which has a substantially circular section can be used. With this, the manufacturing cost can be reduced and the manufacturing can be facilitated. Still, when the protruding portion (rotation-preventing means) which projects convexly in part and outwardly in the radial direction is formed in the flange-shaped peripheral edge, the number of the protruding portion may be one or more.
The present invention described above can be specified in the following inflator.
Namely, an inflator has an inflator housing containing a pressurized medium charged therein, a gas generator which comprises the gas generator housing in communication with the inflator housing and a propellant arranged inside the gas generator housing, an outlet passage which makes either space inside the inflator housing or gas generator communicate with the diffuser assembly, a first closing disk sealing the outlet passage, a projectile arranged and adjusted for the first closing disk and a combustion-product forming means which forms a combustion product for igniting the propellant. The projectile is propelled to pass through at least partially the first closing disk by using the combustion-product forming means, and the outlet passage is arranged inside the inflator housing to extend, passing through one end of the inflator housing and is at least partially arranged and adjusted for the gas generator housing. Also in the inflator, the stud bolt is inserted from the inside of the diffuser assembly to be supported and fixed, thereby preventing the inflator from being dislocated out of the module case.
When an inflator according to the present invention is used in a pad module for an air bag apparatus comprising the inflator, an air bag which introduces a gas generated due to activation of the inflator therein to inflate the air bag, and a module case which accommodates the inflator and the air bag, the pad module prevents the inflator from being dislocated due to vibrations or the like.
Further, in the pad module for an air bag apparatus, when a rotation-preventing means, serving at a time of assembling of the inflator, is formed on a flange-shaped peripheral edge of the boss member in the inflator and/or an insertion portion for the inflator of the module case, is facilitated, manufacturing cost can be reduced.
That is, the inflator comprises a boss member closing one end opening of the inflator housing, a peripheral edge of the boss member is formed in a flange shape projecting and spreading in the radial direction of the inflator housing, and the flange shaped-peripheral edge is provided with a rotation-preventing means projecting outwardly in the radial direction. Meanwhile, in the module case, an opening portion for inserting the inflator into the inner space is formed and a supporting portion for abutting/supporting the rotation-preventing means is provided on a peripheral edge of the opening portion, thereby forming a pad module for an air bag apparatus in which the rotation-preventing means is supported by the supporting portion.
According to the present invention, damages to the connection structures of the inside and outside of inflator or the like can be prevented, and reliability at the time of activation of the inflator can be improved. Also, reliability at the time of mounting to a vehicle and an assembling easiness can be enhanced.
Furthermore, the entire weight and size of the inflator itself can be suppressed by reducing the number of constituent parts, and the inflator is advantageous in terms of cost by enhancing a manufacturing efficiency.